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Title: An investigation into the fatigue damage development in open- and bolted-hole composite laminates
Author: Nixon-Pearson, Oliver James
Awarding Body: University of Bristol
Current Institution: University of Bristol
Date of Award: 2013
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There is a significant amount of work in the open literature regarding final failure of notched composite laminates, however there has been rather less characterisation of sub-critical damage prior to final failure, particularly under fatigue loading conditions_ A previous investigation into the static tensile strengths of scaled open-hole specimens showed three distinct failure modes which were either matrix- or fibre-dominated. Three open-hole specimen configurations which exhibited clear examples of these failure modes were chosen for the fatigue investigation. The primary objective of this thesis was to introduce a detailed experimental investigation into the sub-critical damage prior to specimen failure by interrupting fatigue tests part way through the decrease in stiffness with increasing number of cycles. X-ray computed tomography (CT) was carried out for the interrupted test specimens in order to establish the damage development. In some cases a different failure mode is observed under fatigue loading to the quasi-static cases. It is shown how the role of delamination is critical in fatigue even when it may not dominate in quasi-static tests. Cohesive element models in finite element analysis have been shown to be effective at predicting delamination failure, including fatigue formulations. These have largely been applied to simple configurations such as the Double Cantilever Beam (DCB) specimen. The University of Bristol fatigue cohesive formulation has been applied to models of the open-hole tests to predict the damage seen in interrupted fatigue test specimens. This is the first such application of fatigue cohesive element models to complex cases involving matrix cracks, delaminations and their interactions.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available